1. Field of the Invention
The invention relates to an electronic device for electrically connecting a power supply and data transmission system and at least one actuator and/or sensor, including a two-pole system and device terminal, a two-pole power supply output, and having data separation or decoupling between the two-pole system, the device terminal and the power supply output. The device further includes a data processor electrically connected to the two-pole system and the device terminal, and including at least one choke as data separation or decoupling between the two-pole system, the device terminal and the power supply output. The invention relates to a hardware component of the system under discussion, specifically to the electronic device which is called the slave (or ASI slave) in this system.
2. Description of the Prior Art
Under the name xe2x80x9cactuator-sensor interface or xe2x80x9cASIxe2x80x9d eleven well-known actuator, sensor and control manufacturers and two institutions of higher education have developed a system of hardware components which are connected via three interfaces among one another and with their environment (See, ASI The Actuator-Sensor Interface for Automation, by Prof. Dr. W. Kriesel and Dr. O. W. Madelung, published in 1994 in Carl Hanser Verlag, Munich and Vienna, and the 2nd revised and expanded edition of this book published in 1999). The hardware components of this system include a transmission system, slaves and at least one master. In the system under discussion, the transmission system, also called the ASI line, is used for power supply of the slave (and thus, the actuators and sensors connected to the slaves) and for power supply of the master and for data transmission between the slaves among one another and between the slaves and the master.
The electronic device is called the slave (or ASI slave), and represents the connecting component between a power supply and data transmission system and an plurality of actuators and sensors. The electronic device may take the form of a separate device which is connected to the power supply and data transmission system and to which at least one of the actuators and the sensors are connected. In terms of hardware engineering, however, it can also be such that a slave, an actuator and a sensor, or a slave, at least one of a plurality of actuators and several sensors are combined to form the electronic device. The electronic device includes a two-pole system and device terminal with which the power supply and data transmission system are connected to the electronic device and the electronic device to the power supply and transmission system, a power supply output for power supply to the actuators and/or sensors, in the indicated citation called Uout and 0 V, data separation and decoupling between the system and device terminal and the power supply output thereto, which separates the power path and the data path from one another.
The power supply or part of the power supply, data processing electronics connected to the system and device terminal, which includes a transmitter, a receiver, a sequence control system and a nonvolatile memory, and a multi-pole data input and output which is connected to the data processing electronics. The slaves and the master are designed such that data is generated and exchanged in the form of a data telegram via the power supply and data transmission system. This results in the fact that the slaves should take only a limited current from the power supply and data transmission system, and the impedance behavior of the slaves over frequency should not fall below a boundary curve. In the such a system, the slaves consist of a highly integrated circuit and a few external components. A power supply voltage between 19 V and 25.6 V at a maximum current of 35 mA is made available, which is sufficient for some actuators and for most of the sensors. If greater currents are necessary, a parallel branch is set up which makes available the increased current. Data separation or decoupling is accomplished by chokes which are electronically simulated in the integrated circuit or when higher currents are necessary, by chokes as external components.
The conventional electronic device of the prior art, therefore, the slaves (ASI slaves), have limited applicability in two respects. Firstly, the actuators and sensors to be connected should not have an impedance such that the impedance behavior over frequency falls below the stipulated boundary curve. Secondly, the possible power supply, whether voltage or current, is insufficient or at least problematical, especially for certain actuators. The limited applicability of the slaves becomes relevant especially when solenoid valves are to be connected as actuators.
It has been formulated to enhance the capability of conventional electronic devices, in particular, the slave for connecting a controllable, additional impedance in series to one pole of a power supply output. This makes it possible to connect to the electronic device and those actuators which must not be connected to conventional electronic devices, therefore, to the slaves described in the prior art, because due to such a connection, the impedance behavior of the device over frequency would fall below the stipulated boundary curve so that data transmission would no longer work properly. With respect to the details of the aforementioned teaching xe2x80x9cseries connection of a controllable additional impedancexe2x80x9d, reference is made to German Patent Publication 196 39 379.
In conventional electronic devices, a current of 0.2A can be taken from the power supply and transmission system. There are two chokes in these devices as data separation and decoupling and the chokes, of which each has an inductance of approximately 5 mH, a resistance of approximately 5 ohms and a resonant frequency which is greater than 500 kHz, are in series and in series to the connected load when the load is connected to the power supply output. The electronic devices described above with respect to their data separation and decoupling are problematical in two completely different respects. Firstly, in current ASI systems thirty one electronic devices (slaves) can be connected to the power supply and data transmission system. ASI systems with an expanded address range are used so that instead of thirty one slaves, sixty two can be connected. This, of course, leads to the requirement that the minimum impedance of the individual slaves must be doubled. Secondly, the electronic devices allow a current of only, 0.2A, however, it is desirable to allow a higher current such as 0.4A to 0.6A. The two problems could be satisfied by increasing the number of chokes used for data separation and decoupling, thereby, doubling the minimum impedance by connecting each choke in series to another choke of the same design. However, this would lead to doubling of the resistance, and thus, to doubling of the heat loss or power loss which has taken place in the electronic devices, thereby resulting in an undesirable increase in temperature of the electronic device.
If the intention is to build devices which allow a current of 0.4A, a total of eight chokes are necessary, in each branch two chokes in series, to which two other chokes at a time must be connected. In building devices which allow a current of 0.6A, eighteen chokes are necessary. (In the aforementioned it has been considered that the current which flows via the choke, when economical standard chokes are to be used, may not exceed a value of roughly 0.2A). If the above described measures were used cumulatively in the described manner, if both the address range were to be expanded and also the current load capacity were to be increased, sixteen chokes (for a current of 0.4A) or even thirty six chokes (for a current of 0.6A) would have to be installed, which would lead to devices which would be too expensive, too large and too hot.
In view of the foregoing, an object of the present invention is to provide an electronic device with expanded applications such that an expanded address range and a higher current load capacity will be possible.
The electronic device in accordance with the present invention, the aforementioned object is characterized in that an isolation amplifier circuit which is effective only for AC voltage is connected in parallel to the choke. The electronic device in accordance with the present invention is data separation and decoupling, whereby preferably at least one choke is data separation and decoupling. Regarding the function of data separation and decoupling, the component xe2x80x9cdata separation or decouplingxe2x80x9d is one which should have a relatively great alternating current impedance, but a relatively small direct current resistance for the frequency range under consideration. While, one such component with the corresponding dimensioning is a choke, other components are also conceivable which have a relatively large alternating current impedance and a relatively small direct current resistance. Accordingly, with respect to the electronic device in accordance with the present invention, this means that parallel to the choke an isolation amplifier circuit which is effective only for AC voltage is connected, thereby requiring no need for at least one choke as data separation or decoupling. Rather, for explanation, the expression xe2x80x9cchokexe2x80x9d is only being used because such a devise is apparent to one skilled in the art.
As previously stated, the electronic device in accordance with the present invention is characterized essentially in that an isolation amplifier circuit which is effective only for AC voltage is connected parallel to the choke. An isolation amplifier circuit which is effective only for AC voltage means any component or any circuit to which it applies that the output side AC voltage xe2x80x9cfollowsxe2x80x9d the input-side AC voltage. An isolation amplifier circuit of the type under consideration is, therefore, always present when there is very little or no AC voltage between the output of the isolation amplifier circuit and the input of the isolation amplifier circuit. An important aspect of the present invention is to electrically connect an isolation amplifier circuit which is effective only for AC voltage parallel to the choke, generally parallel to the data separation or decoupling. This leads to the fact that either only very little or no alternating current flows via the choke, generally via the data separation or decoupling. The parallel connection of the choke and the isolation amplifier circuit which is effective only for AC voltage is, therefore, a component which has a large alternating current impedance, but a small direct current resistance. In particular, there are now various possibilities for embodying and developing the electronic device in accordance with the present invention.